During the drilling and completion of an oil well where a borehole traverses earth formations, it is customary to install one or more liners (tubular strings of pipe) in the borehole where the liners are cemented in the borehole by filling the annulus between the liner and the borehole with cement. In installing a liner (which is a string of pipe), the upper end of the liner is connected to a tubular liner hanger which typically has circumferentially arranged exterior slip or wall engaging members where the slip members are in a retracted condition while the liner hanger is lowered into the borehole. The slip members can be set to engage a wall by either hydraulically actuated means or mechanical mechanisms and the liner hanger usually has an interior left-hand thread which is used for releasably coupling the liner hanger to a tubular setting tool. The setting tool has a matching left-hand threaded release nut for coupling with the liner hanger and has a supporting tubular mandrel with a non-circular exterior portion which is slidably but non-rotatably connected in the bore of the release nut. Below the release nut the supporting mandrel has a load supporting cylindrically shaped, upwardly facing shoulder which engages the release nut so that the weight of the liner is carried by the nut on the mandrel shoulder. The upper end of the setting tool mandrel is connected to a string of pipe which is used to lower the liner and the liner hanger into position in the borehole. While lowering the liner into the borehole it is sometimes desirable to rotate the liner in a right hand direction. This requires an ability to impart rotation to the liner hanger through the setting tool without releasing the release nut. This type of rotation can be accomplished by utilizing a set of longitudinal interengaging splines located between the liner hanger and setting tool mandrel in a well known manner.
When a liner hanger is lowered to a position adjacent to the lower end of the next above casing or liner, the slip members on the liner hanger are set to engage with the surrounding pipe wall. Setting of the slip members can be accomplished by hydraulic actuation or by mechanical actuation.
A hydraulically operated liner hanger utilizes hydraulic pressure in the string of pipe and in the setting tool to actuate an axially movable hydraulic cylinder which moves and causes the slip members on the liner hanger to extend outwardly into gripping engagement with the wall of the surrounding casing or liner. In a mechanically actuated liner hanger, a friction block means on the liner hanger frictionally engages a casing or liner so that an interconnecting "J" slot release mechanism can be operated by manipulation of the setting tool to permit the slip members to be set.
If splines are used in the setting tool to enable rotation of a liner prior to the setting of the liner hanger slips, the splines in the setting tool are disengaged after the liner hanger slips are set by longitudinal movement of the supporting string of tubing. The non-circular portion of the mandrel permits longitudinal movement of the setting tool mandrel with the string of tubing. After disengaging the setting tool splines, right-hand rotation of the string of tubing releases the threaded release nut from the interior threaded connection with the liner hanger. The setting tool in a released position in the liner hanger also has pressure sealing means located in the bore of the liner hanger so that the string of tubing is in fluid communication with the bore of the liner. In this condition, before removing the released setting tool from the liner hanger, a cement slurry is pumped down the string of tubing and the liner bore and into the annulus between the liner and the borehole.
The cement slurry which is introduced to the annulus moves upwardly in the annulus between the liner and the borehole. As the cement slurry travels upwardly in the annulus, it displaces the drilling mud in the well bore above the cement. If the liner is reciprocated and/or rotated during the cementing operation, this movement will greatly assist the obtaining of a uniform distribution of the cement in the annulus and proper displacement of the drilling mud in the annulus without channeling of the cement through the mud.
In recent years liner hangers have incorporated a rotatable bearing between horizontal load bearing surfaces in the liner hanger so that when the slips of the liner hanger are set and the liner is suspended by the liner hanger slips from the next above string of well pipe, the liner is supported in the liner hanger on a rotational bearing. The rotational bearing then facilitates rotation of the liner relative to the liner hanger after setting the liner hanger slips. Examples of rotatable load bearing bearings and liner hangers are shown in U.S. Pat. No. 4,033,640 and U.S. Pat. No. 4,190,300.
In order to rotate the liner during the cementing operation, the released setting tool must be coupled to the liner hanger so that rotation of the string of tubing can permit the liner to be rotated as much as desired during the cementing operation. It is desirable that the setting tool remain released from the liner hanger so that it can be pulled out of the well by an upward movement of the drill string at any time during the operation.
Prior art systems for rotating liner hangers and setting tools prior to setting of the slips are well known and typically utilize a single set of splines. In U.S. Pat. No. 4,562,889, and co-pending patent application Ser. No. 609,104, filed May 10, 1984, dual spline arrangements are shown where a second set of splines can be engaged upon release of the release nut so that the liner and setting tool can be co-rotatively rotated while the release nut is released. These systems however require extra spline housing components in the liner hanger and a special setting tool which does not have a universal use.
When the liner hanger for the liner is set in the casing, it is set so the bottom of the cement shoe on the liner is just located above the bottom of the borehole a sufficient distance to eliminate the possibility of fouling of the cement shoe orifices and so that the liner hanger slips can engage the next above casing or liner. As may be appreciated, the cementing operation requires considerable care because once the cement slurry is in the annulus, the liner cannot be removed and repositioned since the cement is already in place. Also, if the releasing mechanism in the setting tool is not disengaged from the liner hanger prior to the cement slurry hardening up, the drill string can be hung up in place. Such malfunctions can result in the loss of well equipment in the well or even destroying the well.